Obstruction square



FIG. 1 is a three dimensional perspective view of the obstruction square of this design illustrating the cutaway portion to overcome corner obstructions;

FIG. 2 is a side view of the obstruction square illustrating the cutaway portion to overcome corner obstructions;

FIG. 3 is a top view of the obstruction square; and,

FIG. 4 is a front view of the obstruction square. 

The ornamental design for an obstruction square, as shown and described. 